The present invention relates to the use of irrigation sprinkler controllers. More particularly, the invention relates to the reception and use of Evapotranspiration data by irrigation sprinkler controllers.
Irrigation is the artificial application of water to soil to promote plant growth. The practice dates back at least to the canals and reservoirs of ancient Egypt. Today, farmers and others irrigate hundreds of millions of acres of farmland throughout the world, most notably in the U.S., India, Pakistan, China, Australia, Egypt, and the USSR.
In the past, irrigation sprinkler controllers were often unwieldy and expensive. As a result, many agriculturalists erred in the direction of overwatering their crops to provide a margin of safety. Although overwatering adequately protects the crop investment, increased public concern over water consumption requires that agriculturalists cease this wasteful practice.
Modern methods have brought an increasing measure of control over the rate and timing of irrigation. Recent advances allow agriculturalists to make cost-effective timing adjustments on many remote sprinkler controllers.
Marian (U.S. Pat. No. 4,962,522), issued to the present inventor, exemplifies modern designs for irrigation control systems. The present description incorporates Marian by reference. Marian provides an apparatus and method for remotely controlling irrigation at one or more sites. The user need only periodically calculate an adjustment value to change preset values and then inform a central system. The central system, in turn, delivers the adjustment information via transmissions at commercial paging frequencies to individual sprinkler controllers.
Modernly, an agriculturalist calculates the proper sprinkler adjustment value by referring to Evapotranspiration (ET) data. The ET value represents the total water loss from the soil and vegetation over a predefined period. This water loss includes water lost by direct evaporation and by transpiration from the plant surfaces.
Thus, the ET value provides an indication of an amount of water that an irrigation system must replenish to maintain the plants in an unstressed condition. The ET value, often expressed in inches of water, depends on local weather information. A large state, such as California, can have thousands of different ET zones, each having its own dynamic ET values.
Measurement of water loss for one particular plant species established a normalized ET value. Each plant material has a crop adjustment value used to scale the normalized ET value. The scaled normalized ET value customizes the ET value for each particular plant species. An example of a common crop adjustment value used with ET values is a crop coefficient (K.sub.c). The crop coefficient (K.sub.c), expressed as a percentage, scales a particular ET value to provide a water quantity for the particular crop. The crop coefficient (Kc) can vary over time, depending upon particular seasons and a plant's water requirement for flowering or bearing fruit, for example. A number of references: Blaney, H. F., et al., (Aug. 1950), "Determining Water Requirements in Irrigated Areas from Climatological and Irrigation Data," U.S. Dept. of Agri. Soil Conserv. Service, pp. 1-48; Penman, H. L., (1948), "Natural Evaporation from Open Water, Bare Soil and Grass," Proceedings, Royal Soc., Series A., Vol. 193, pp. 120-145; Jensen, M. E., (Dec., 1963), "Estimating Evapotranspiration from Solar Radiation," J. Irrig. and Drainage Div., pp. 15-41; Jensen, M. E., (Sep., 1983), Design and Operation of Farm Irrigation Systems,"Am. Soc. Agri. Eng., No. 3, pp. 1-232; and "How Much Water Does Your Lawn Really Need," Sunset, (Jun. 1987), pp. 213-219; hereby incorporated by reference for all purposes, are suitable as a background source on ET and calculation of ET values.
ET has rapidly become a water-use standard--regulatory bodies in some areas demand that agriculturalists conduct irrigation only through use of ET values. In such areas, harsh penalties attach to water use which exceeds ET values. Such penalties provide impetus for users to limit their water use.
Many local variables, including temperature, humidity, wind, net solar radiation, soil temperature, and precipitation can affect the calculation of the ET value for a particular zone. Accordingly, agriculturalists must get extremely detailed and accurate weather profiles at regular intervals. Fortunately, governmental agencies usually provide ready access to ET information to users in states which are heavily dependent on irrigation. The government provides for user access to the ET data in several ways.
One avenue of user access to local ET data involves use of a personal computer and a modem to connect to a central government database. This user-intensive procedure requires the user to gain access to ET information and then to calculate the sprinkler adjustment value for each controller. If users have extensive irrigation requirements that span several ET zones and employ many controllers, this method can be time-consuming and error-prone.
Another avenue for supplying ET information is for local water control agencies to provide such information via daily phone recordings. Still another method of distributing ET values is publication in local newspapers or other periodicals. Again, these methods require a user to gain access to information and to calculate the adjustment value. Any particular publication may not cover ET zones that are not in a local area. The user must still search out the information, perform necessary calculations, and manually enter necessary changes, for each zone and controller. As the number of zones and the concomitant number of irrigation controllers increases, these solutions become increasingly cumbersome and inefficient.
A modern design, such as offered by U.S. Pat. No. 4,962,522 (Marian), represents a significant improvement in the art of irrigation controller design. It is now possible to control remote irrigation controllers daily. Nevertheless, such a controller is still dependent on human interaction, particularly in accessing, extracting and using desired ET values, as modified by the crop coefficient (Kc). The U.S. Pat. No. 4,962,522 patent does not address the problem and does not solve the heavy user demands problem.
A human being must still (1) access current ET information for each controller under his dominion. The user must then (2) calculate (either by hand or processing means) a proper sprinkler adjustment value responsive to the accessed ET data. Finally, the user must (3) enter the latest sprinkler adjustment value to a system for broadcast delivery to a collection of sprinkler controllers.
Thus, modern controllers are still dependent on humans to gain access to ET data periodically, to calculate an adjustment value, and to deliver the adjustment value. In fact, when an agriculturalist must access, calculate, and deliver information to hundreds of sprinkler controllers, such human interaction remains a burdensome and formidable task.
Accordingly, there is a need for an ET-data-based method and apparatus for controlling irrigation through access, calculation, and delivery of ET information to multiple controllers.